The Rapport multimedia conferencing system, disclosed in the S. R. Ahuja et al. article, "The Rapport Multimedia Conferencing System", Proceedings of Conference on Office Information Systems, Mar. 1988, supports interactive, real-time distributed conferences among two or more people. The system provides an environment in which many types of meetings can take place, including telephone conversations, discussion among colleagues, and lectures. Rapport is designed to help people emulate face-to-face conferences as closely as possible with their workstations. A Rapport system user may participate in many conferences concurrently by switching among contexts at the click of a mouse button. This is equivalent to being able to walk in and out of several meeting rooms (and one's office) instantly.
It is anticipated that this capability will encourage users to keep many conferences active for long periods of time in much the same fashion as the use of screen windows allows one to keep many programs and files active with the present data networks. One such long-lived conference might be an intercom connection between a manager and a secretary. Others might be among the collaborators in a design project or the authors of a paper. It is anticipated that once the capability for multiple concurrent calls is provided, it will be useful to merge and split such calls. For example, the manager may ask the secretary to join a design project conference from time to time to assist the project team. In addition to merging and splitting calls, typical applications would include the addition of several parties to a conference, the addition of some parties and the deletion of others, or changing the connectivity pattern among parties, for example, from multipoint-to-multipoint to point-to-multipoint with upstream capability. A general problem associated with these actions relates to the transformation of an original conference connection through a network of switching systems, to a target connection. Although tearing down the original connection and establishing the target connection from scratch will always work, it is not, in general, an efficient approach in terms of the number and complexity of the operations to be performed on the network.
The J. S. Turner article, "Design of a Broadcast Packet Switching Network", IEEE Transactions on Communications, Jun. 1988, discloses a broadcast packet switching network where each broadcast source and its associated connections induce a tree in the network. When a user disconnects from a broadcast channel, the corresponding branch of the tree is removed. When a user requests connection to a channel, the network attempts to find a nearby branch of the broadcast tree and connects the user at the nearest point. The Turner article provides no suggestion, however, concerning efficient network transformation other than the addition or deletion of a single party.
In view of the foregoing, a deficiency in the art is the absence of an efficient general method of transforming an original conference connection through a switching network, to a target conference connection which involves more than the addition or deletion of a single party or user station.